HR: 11:05h
AN: A12B-04    [Abstracts]
TI: Constraining Global Isoprene Emissions With GOME Formaldehyde Column Measurements
AU: * Shim, C
EM: cshim@eas.gatech.edu
AF: Department of Earth and Atmospheric Sciences, Georgia Institue of Technology, 311 Ferst Dr, atlanta, GA 30332 United States
AU: Wang, Y
EM: ywang@eas.gatech.edu
AF: Department of Earth and Atmospheric Sciences, Georgia Institue of Technology, 311 Ferst Dr, atlanta, GA 30332 United States
AU: Choi, Y
EM: yunsoo.choi@eas.gatech.edu
AF: Department of Earth and Atmospheric Sciences, Georgia Institue of Technology, 311 Ferst Dr, atlanta, GA 30332 United States
AU: Palmer, P I
EM: ppalmer@fas.harvard.edu
AF: Department of Earth and Planetary Sciences, Division of Engeering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford St, Cambridge, MA 02138 United States
AU: Abbot, D S
EM: dsa@io.harvard.edu
AF: Department of Earth and Planetary Sciences, Division of Engeering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford St, Cambridge, MA 02138 United States
AU: Chance, K
EM: kchance@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 United States
AB: Biogenic isoprene plays an important role in tropospheric chemistry. Current isoprene emission estimates are highly uncertain due to lack of observations. Formaldehyde (HCHO) is a high-yield product of isoprene oxidation. The short photochemical lifetime of HCHO allows observations of this trace gas to help constrain isoprene emissions. We use HCHO column observations from the Global Ozone Monitoring Experiment (GOME) satellite instrument. These global data are particularly useful for studying the tropics where most of the global budget of isoprene is emitted, and where in situ observations are notably sparse. We present results from an inverse model study that uses GOME data from September 1996 to August 1997 to fit modeled sources of HCHO from the GEOS-CHEM chemistry transport model. Isoprene emissions are divided into 10 vegetation types. Column contributions to HCHO from these 10 biogenic sources, in addition to biomass burning and industrial sources are considered. We fit these 12 sources of HCHO to the observed column data for 8 geographical regions (North America, Europe, East Asia, India, South Asia, South America, Africa, and Australia). The a priori simulation highly underestimates global HCHO columns over the 8 geographical regions (bias: -14 - -46%; R:0.52 - 0.84). The a posteriori solution shows generally higher isoprene and biomass burning emissions. The a posteriori simulation with a posteriori isoprene emissions improved the model bias for all regions (bias: -5.9 - -26%; R = 0.57 - 0.85). The a posteriori estimate of the annual global isoprene emissions of 565 Tg C yr$^{-1}$ is about 50 % larger than the a priori estimate. This increase of global isoprene emissions significantly affects tropospheric chemistry, decreasing the annual global mean OH concentration by 10.8% to 0.95 x 10$^{6}$ (molecules cm$^{-3}$ ) and increasing the annual global tropospheric O$_{3}$ burden by 1.5% to 333 Tg. The atmospheric lifetime of CH$_{3}$CCl$_{3}$ increases from 5.2 to 5.7 years.
DE: 5405 Atmospheres--composition and chemistry
DE: 1704 Atmospheric sciences
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting